Heat transfer apparatus having flexible plastic tubular elements arranged in a braided configuration



3,419,069 TUBULAR Dec. 31, 1968 1:3, BAKER ET AL HEAT TRANSFER APPARATUSHAVING FLEXIBLE PLASTIC ELEMENTS ARRANGED IN A BRAIDED CONFIGURATIONFiled April 28. 1967 Sheet INVENTORS THOMAS BERNARD BAKER STANLEY BURTONLEVY ROLAND FREDERICK OTTOLINI ATTORNEY Dec. 31, 1968 115, B K ET ALHEAT TRANSFER APPARATUS HAVING FLEXIBLE PLASTIC TUBULAR ELEMENTSARRANGED IN A BRAIDED CONFIGURATION Filed April 28, 1967 Sheet FIG.

INVENTORS THOMAS BERNARD BAKER STANLEY BURTON LEVY ROLAND FREDERICKOTTOLINI ATTORNEY United States Patent 3,419,069 HEAT TRANSFER APPARATUSHAVING FLEXIBLE PLASTIC TUBULAR ELE- MENTS ARRANGED IN A BRAIDEDCONFIGURATION Thomas Bernard Baker and Stanley Burton Levy, Wilmington,and Roland Frederick Ottolini, Newark, Del., assignors to E. I. du Pontde Nemours and Company, Wilmington, Del., a corporation of DelawareFiled Apr. 28, 1967, Ser. No. 634,631 Claims. (Cl. 165--158) ABSTRACT OFTHE DISCLOSURE A heat transfer apparatus having a casing membersurrounding at least one bundle of flexible plastic tubular elements, asubstantial portion of each bundle comprising a first group of tubularelements arranged in a given pattern and interlaced in a substantiallyuniform manner with a second group of tubular elements arranged insymmetrically opposed pattern to provide a coherent flexible bundle,stable in size, and having a predetermined degree of packing andpredetermined resistance to fluid flow through said bundle exteriorly ofsaid elements which predetermined characteristics cooperate to provide agood heat transfer characteristics for the apparatus.

Introduction This invention relates generally to improved heat exchange,or heat transfer, apparatus; and more specifically to heat exchangeapparatus having flexible plastic tubular elements in a particularlyadvantageous bundle arrangement.

It is an object of the invention to provide novel and improved heatexchange apparatus combinations or arrangements having plasticcomponents, especially flexible tubular elements, and components made ofmaterials such as metals which arrangements perform effectively,reliably, and in addition, not only accommodate but utilizeadvantageously during their operation, the different properties of theplastic components under the desired operating conditions.

It is a further object to provide such novel and improved apparatuscombinations which will overcome the problems, disadvantages, anddeficiencies of early prior art flexible plastic tube heat exchangeapparatus combinations as will be discussed hereinafter.

Other objects and advantages will be apparent from a consideration ofthe following specification, claims and accompanying drawings.

Background of the invention As indicated generally in US. Patent No.3,228,456, heat exchange arrangements utilizing plastic tubular elementsare known and have been found to be advantageous in many applications.Because of the use of small flexible plastic tubular elements, a numberof special problems have been encountered, not only in designing andproducing such arrangements, but also in their operation. Some of theseproblems involve the relatively low heat transfer coeflicients and therelatively high coeflicients of thermal expansion possessed by mostplastic materials as compared with parts made of more conventional ma-3,419,069 Patented Dec. 31, 1968 terials such as metals. Other problemsrelate to the different properties such as compressive strength, tensilestrength, flexibility, and melting points of these plastic materialsrelative to the other materials used. Production and operatingtechniques as well as apparatus designs must be established such thatthe more conventional parts such as those still for-med of the usualmetallic compositions can be shaped, formed, heated, and used While incooperative association with the plastic parts to produce and operateeconomical, reliable, and effective heat exchange arrangements Wit-houtdestroying or damaging the associated plastic parts by application ofexcessive forces, impacts, temperatures, or other conditions.

One problem involves maintaining uniform packing and resistance to fluidflow for the tube bundle in plastic tube heat exchange apparatus. This,in turn, has been related to the flexible nature of the small plastictubes used in this type heat exchanger apparatus. The problem isaggravated at elevated operating temperatures at which considerablethermal expansion takes place and the tubes become even more flexibleand limp. A number of special structural features have been needed andused in the past to try to solve these problems. One of such features asdisclosed in prior US. Patent No. 3,228,456 involves the use oftransverse rigid baflle members through which the plastic tubularelements extend for lateral support. The baflle members also are neededto provide the desired fluid flow conditions exteriorly of the tubularelements. A second of such features as disclosed in prior US. Patent No.3,277,959 involves the use of interleaved tape elements spaced along abundle of plastic tubular elements and bonded thereto. The tape elementsposition the tubular elements, maintain them in a fairly compact bundle,and control, to some extent, fluid flow conditions exteriorly of thetubular elements in the bundle. A third feature of this type asdisclosed in prior copending application Ser. No. 598,070, filed Nov.30, 1966 in the name of Robert Dilman Smith involves placing a bundle ofplastic tubular elements in a foraminous casing member or sleeve tomaintain a compact bundle configuration and desired fluid flowconditions in the bundle exteriorly of said elements.

However there are serious problems and disadvantages associated witheach of the above prior art features. For example, threading the greatmultiplicity of small tubular elements through perforated transversebaffies as mentioned in the feature first mentioned is a prohibitiveoperation as to cost and time, and in addition does not prevent thesqueezing together and spreading apart of the flexible tubular elementsbetween the spaced transverse baflle members, which has an adverseeffect on fluid flow conditions and on the tubular elements.

As to the second feature mentioned above, the spaced tape elementsbonded to the tubular elements, prevent bending of the bundles duringproduction, and use and will break loose or damage the tubular elementsif excessive bending forces are encountered. In addition, the tapes donot prevent the squeezing together and spreading apart of the flexibletubular elements between the spaced tape elements which has an adverseeffect on fluid flow conditions and on the tubular elements. The

bonding of spaced tape elements to the tubular elements tubularelements, does reduce the spreading apart of the tubular elements butstill requires spacing means such as the tape elements to maintain thedesired spacing between the tubular elements. Squeezing together of thetubular elements between the tape element positions still occurs andthis feature represents a costly, and not entirely successful, way toprovide a compact bundle with uniform spacing and resistance to fluidflow through the bundle.

In applicants improved arrangement embodying the present invention, theflexibility of the plastic tubular elements is used to provide a bundleof uniformly interlaced tubular elements which, without any additionalstructure or means, results in a coherent compact bundle in whichuniform packing, resistance to flow, and spacing of the tubular elementsare maintained uniformly along the bundle. In addition, the bundle isflexible and rugged as required in assembly and operation of the heatexchange apparatus, and also accommodate thermal expansion of theelements in a more uniform and controlled manner. Where the bundles areprovided in the preferred form of sleeve-like configurations it ispossible without difficulty to assemble a number of sleeve-like bundlesone inside the other and, if desired, to provide additional supportand/or fluid flow for the bundle by positioning a substantially rigidsupport or a sparger member within the bundle as will be described indetail hereinafter.

In the drawings:

FIGURE 1 is a partial isometric view of a preferred heat transferarrangement embodying features of the invention with certain partsbroken away to show the relationship of the component parts andfeatures.

FIGURE 2 is a side elevational view, with certain parts broken away fora clearer showing, of a somewhat different heat transfer arrangementembodying features of the invention.

FIGURE 3 is an enlarged end view of the sparger and support member ofthe arrangement of FIGURE 2.

FIGURE 4 is a partial side elevational view of a bundle of tubularelements with the cooperating tube sheet member and a rigid support andsparger member associated therewith. The interlaced arrangement of theflexible tubular elements embodying the present inven tion is also shownin this figure.

FIGURE 5 is a partial enlarged detailed view of the preferred interlacedflexible tubular element arrangement of the invention, showing how theimportant angle of tubular element cross over or intersection ismeasured.

FIGURE 6 is a partial transverse cross sectional view of the arrangementof FIGURE 4 taken at line 66.

FIGURE 7 is a partial longitudinal cross sectional view of the spargerand support member of FIGURE 3.

FIGURE 8 is an enlarged partial side elevational view Of a heat exchangearrangement embodying features of the invention and similar to that ofFIGURE 4, showing a modified arrangement in the tubular elements areinterlaced With each other in groups of four.

One preferred heat exchange arrangement or combina: tion embodyingprinciples of this invention is shown in FIGURES l, 4, 5 and 6. Theapparatus shown in these figures comprises a casing member 10 formed bywall elements 11 of suitable material which define a chamber for a fluidthe upper surface of which is indicated at 14. The casing member isprovided with fluid inlet means 12 and fluid outlet means 13. Anelongated compact bundle of a relatively large number of smallthin-walled flexible plastic tubular elements T is positioned as shownto extend through at least a portion of a fluid in the chamber definedby wall elements 11. Each end of the bundle 20 is provided with a headerunit 21 which maintains free communication between the interiors of thetubular elements T and fluid supply conduit elements 23, 24, 25.Suitable header unit arrangements are shown for example in U.S. Patents3,228,456 and 3,277,959 mentioned above. The tubular elements T of whichthere may be from about 500 to about 10,000 or more, may be formed of acomposition, and in sizes, disclosed in the abovemen-tioned U.S. PatentNo. 3,228,456. The composition preferred is a polyfluorinated plasticsuch as a copolymer of tetrafluoroethylene and hexafluoropropylene witha thermal conductivity of about 0.1 B.t.u./hr./ft./F. The tubularelements in the bundle are preferably in a size range between about 5and 275 mils outside diameter with a wall thickness between about 0.5and about 30.0 mils on centerlines spaced in an average of about 1.01-2.00 diameters.

As best shown in FIGURES 4, 5 and 6, the position of the tubularelements relative to each other, the packing of the tubular elements,and their resistance to fluid flow are controlled solely by theinterengagement and interlacing of the flexible tubular elements witheach other. A braided arrangement, as shown in FIGURES 4, 5 and 6 ispreferred in which a plurality of braided sleeves are assembled oneinside the other to form the bundle. Generally speaking, each sleevecomprises a first plurality of tubular elements positioned in a firsthelical pattern and an interengaged interlaced second plurality oftubular elements positioned in a second opposing helical pattern. In thepreferred interlaced pattern shown in the drawings a tubular element ofone plurality proceeds in an over two and under two pattern ofinterweaving relative to the tubular elements of the second opposingplurality, with the interwoven position of any element being offset byone element with respect to its adjacent tubular elements of the sameplurality. Another variation of an interlaced bundle is shown in FIGURE8 in which the tubular elements are interlaced in the same generalmanner except that they are handled in groups of four elements. If thetubular elements are interwoven or braided together too tightly, aclosed pattern with prohibitive resistance to fluid flow, unacceptablesusceptability to plugging, and undesirable kinking of individualtubular elements is formed. On the other hand, if the tubular elementsare interwoven or braided together too loosely, the bundle loses itsdesired coherence and compactness; also, the position of the elementsrelative to each other to maintain a desired uniform packing packing andresistance to fluid flow through the bundle cannot be established ormaintained. It has been determined that a controlling factor is the.angle of intersection formed where tubular elements of one pluralitycross over the elements of the other plurality. For tubular elements inthe size ranges discussed above, and particularly for tubular elementsof about mils outside diameter, this angle is preferably maintainedbetween about 10 and about 60. The measurement of this angle is shown inFIGURE 5 at angle ABC or 0.

Formation of the interwoven bundles or sleeves is suitably accomplishedon conventional well-known brading machinery with a few minormodifications obviously necessary to adapt them from small solid wiresor yarns to the small hollow tubular elements utilized in the apparatusof this invention. One example of a satisfactory arrangement generallysuitable for forming the interlaced bundles of this invention isdisclosed in Catalog 56 (ELF-20004-1M-l164) on Braiders of the NewEngland Butt Co., 304 Pearl Street, Providence, R.I. Preferably, braidedor interlaced bundles are formed with end portions in which the tubularelements are substantially parallel (not interlaced) to facilitateconstruction of the tube sheet TS (FIGURE 4) or end constructionsuitable for forming the necessary header arrangement of a heat exchangeapparatus (such as disclosed in abovementioned U.S. Patents 3,228,456and 3,277,959). This is accomplished by periodically ceasing thebraiding or interlacing action as a long length of bundles of tubularelements is being produced.

As shown in FIGURES 1, 4 and 6, the configuration and/ or position ofthe bundle of tubular elements as a Whole can be controlled ormaintained by the use of a rigid unit inserted within the bundle. Thisunit may, if desired, be hollow and provided with suitable orifices 33so fluid can be circulated through the unit into the bundle to improvefluid circulation and distribution within the bundle. Specifically, inFIGURE 1 the unit 32 in a U-shaped configuration within the bundlemaintains the bundle configuration and position. Unit 32 is connected toconduit elbow elements 31 and to other conduits elements 30 and 33through which fluid is supplied into the bundle interior as shown. Asfurther illustrated in FIGURE 1, the tube bundle 20 and rigid supportingunit 32 are held in position relative to each other and relative to thewall elements 1 1 of the housing by means of a bracket assemblycomprising elements 40, 42, and 43, all held in place by bolts 44 and41. In FIGURE 4 the rigid unit controlling the position of the bundleand improving fluid circulation comprises a hollow radial portion 310and a hollow axial portion 312 having perforations or orifices 313.

In operation of the apparatus of FIGURE 1, a fluid at one temperature ispassed through the housing by means of inlet 12 and outlet 13, while asuitable fluid at a significantly different temperature is passedthrough the tubular elements T of bundle by means of conduit elements23, 24, and header units 21 to cause transfer of heat between the twofluids. In order to improve the fluid flow through the bundle 20exteriorly of the tubular elements, a portion of the fluid at said onetemperature may be circulated through the hollow rigid unit 32 and outof orifices 33 by means of supply conduit elements 33 and 30.

A modified version of heat transfer apparatus embodying principles ofthe invention is shown in FIGURE 2. This version corresponds to atube-in-shell heat exchanger arrangement similar to that shown in theabove mentioned US. Patent No. 3,228,456. In this version, braided orinterlaced bundle of tubular elements similar to that shown in FIGURE 4has been positioned in a shell or casing member 101 which is providedwith inlet 105, outlet 106, and suitable header units 102 at each endthereof to permit circulation of fluid fro-m inlet 103 through theinteriors of the tubular elements to the outlet 104. Suitable headerconstructions are disclosed in the above-mentioned US. Patents 3,228,456and 3,277,- 959. If desired, a rigid unit 401 can be mounted incooperation with shell inlet 105 as shown in FIGURE 2 and in engagementwith the bundle of tubular elements to help maintain the position of thebundle and improve the handling of fluid supplied into the bundle asshown, by means of openings 403 and 404- in hollow unit 401. Theenlarged showings of FIGURES 3 and 7 make the structure and function ofthis unit clear. Unit 401 functions as shown in the preferred version ofFIGURE 2 to receive a portion of the inlet stream to the shell in itshollow portion, and conduct this portion of the inlet stream directlyinto the central portion of the tube bundle where it is distributedthrough openings 403. The other portion of the shell inlet stream passesthrough openings 404 directly into the shell outside of the hollowportion of unit 401. The direction of shell inlet flow is generallyindicated by the arrows in FIGURE 7. The op eration of the FIGURE 2version of the apparatus of the invention is believed to be apparentfrom the drawing; one fluid at a given temperature being passed withinthe casing member or shell 101 exteriorly of the tubular elements frominlet 105 to outlet 106 while a fluid at a different temperature ispassed from header inlet 103 through the interiors of the tubularelements T to header outlet 104.

It is believed that the preceding description indicates that a novelimproved heat exchanger apparatus has been provided in accordance withthe objects of the invention.

Compared with the above-mentioned prior art heat exchanger combinations,this invention provides a simplified arrangement in which the flexibletubular elements themselves act as spacing means to maintain theposition of the elements relative to each other along the bundle, andestablish a substantially uniform packing and resistance to fluid flownecessary for good heat exchange relation ships. The invention providesa compact bundle which is also flexible and widely manipulatable inassembly, operation, and maintenance while preserving generally theimportant relationships of the tubular elements relative to each other.The new arrangement of this invention results in a heat exchangerapparatus which is less susceptible to plugging of shellside fluid flow,less susceptible to tubular element kinking or damage, and alsoinherently possesses better and more uniform heat transfercharacteristics.

Although certain preferred embodiments of the invention have beendescribed in detail in accordance with the Patent Law, many variationsand modifications within the spirit of the invention will be obvious tothose skilled in the art and all such are considered to fall within thescope of the following claims.

What is claimed is:

1. An improved heat exchanger apparatus comprising in combination: acasing member, said casing member provided with structure defining afluid-containing chamber, said apparatus further comprising a bundle ofsmall diameter, thin-walled, flexible, tubular elements havingcontinuously hollow interiors and formed of an organic polymericcomposition, said bundle extending through at least a portion of saidchamber to cooperate with a fluid contained in said chamber, saidapparatus further comprising supporting means cooperating with saidbundle to support said bundle in said chamber, conduit means operativelyconnected with the interiors of said tubular elements to circulate afluid therethrough and establish a heat transfer relationship with afluid in said chamber, said bundle having at least a substantial portionthereof comprising a first plurality of tubular elements arranged in agiven pattern, and a second plurality of tubular elements arranged in asimilar opposed pattern, said elements of each plurality beinginterlaced in a substantially uniform manner to provide a coherentflexible bundle substantially stable in size, the extent of interlacingand number of tubular elements being such that a predetermined degree ofpacking and a predetermined resistance to fluid flow through said bundleexteriorly of said tubular elements, is provided to maintain said heattransfer relationship at effective levels.

2. The improved apparatus of claim 1 in which the tubular elements ofone plurality cross over the engaged tubular elements of the otherplurality to form included angles of intersection of between about 10and 60.

3. The improved apparatus of claim 2 in which said first and secondpluralities of tubular elements are arranged in symmetrically opposedpatterns and are interwoven in a regular pattern to provide a braidedbundle.

4. The improved apparatus of claim 3 in which said bundle comprises anumber of layers each having interlaced pluralities of tubular elements.

5. The improved apparatus of claim 4 in which said layers are in theform of hollow sleeve arrangements of graduated sizes each positionedwithin sleeve arrangement of larger size to form a compact stablebundle.

6. The improved apparatus of claim 5 in which said bundle is elongatedin form with end portions and the tubular elements at said end portionsare substantially parallel and free of interlacing.

7. The improved apparatus of claim 1 in which the said supporting meanscomprises a substantially rigid reinforcing unit extending through saidbundle and interengaged with said tubular elements to maintain theposition of said bundle within desired limits in said chamber.

8. The improved apparatus of claim 7 in which said unit comprises afluid passageway therethrough and orifices connected therewith forhandling fluid supplied into said bundle exteriorly of said tubularelements.

9. The improved apparatus of claim 8 in which said unit is engaged andcoextensive with a significant portion of the length of said bundle tomaintain the desired position of the bundle and improved fluidcirculation along said portion of the bundle length.

10. The improved apparatus of claim 5 in which said supporting meanscomprises an elongated substantially rigid unit projecting into andextending along within the innermost sleeve arrangement for asubstantial portion of the length of the bundle in order to positivelymaintain the position and configuration of the bundle Within desiredlimits, said unit comprising a fluid passageway therethrough andorifices connected therewith for handling fluid supplied into saidbundle exteriorly of said tubular elements.

ROBERT A. OLEARY, Primal Examiner.

10 A. W. DAVIS, JR., Assistant Examiner.

U.S. Cl. X.R.

